Geography
According to the U.S. Census Bureau, the county has a total area of 1,792 km² (692 mi²). 1,650 km² (637 mi²) of it is land and 142 km² (55 mi²) of it is water. The total area is 7.94% water.

Demographics
As of the census of 2000, there are 45,417 people, 16,765 households, and 12,188 families residing in the county. The population density is 28/km² (71/mi²). There are 19,191 housing units at an average density of 12/km² (30/mi²). The racial makeup of the county is 96.06% White, 0.30% African American, 1.51% Native American, 0.26% Asian, 0.02% Pacific Islander, 0.21% from other races, and 1.64% from two or more races. 0.59% of the population are Hispanic or Latino of any race.

There are 16,765 households out of which 37.70% have children under the age of 18 living with them, 58.40% are married couples living together, 9.90% have a female householder with no husband present, and 27.30% are non-families. 20.60% of all households are made up of individuals and 8.40% have someone living alone who is 65 years of age or older. The average household size is 2.67 and the average family size is 3.08.

In the county, the population is spread out with 28.10% under the age of 18, 7.00% from 18 to 24, 31.40% from 25 to 44, 22.50% from 45 to 64, and 11.00% who are 65 years of age or older. The median age is 36 years. For every 100 females there are 98.50 males. For every 100 females age 18 and over, there are 95.90 males.

The median income for a household in the county is $41,659, and the median income for a family is $46,733. Males have a median income of $32,009 versus $24,078 for females. The per capita income for the county is $17,816. 9.00% of the population and 7.00% of families are below the poverty line. Out of the total people living in poverty, 10.40% are under the age of 18 and 10.30% are 65 or older.